高马赫数V字形钝化前缘平板表面压力特性

Surface Pressure Characteristics on V-Shaped Plates with Blunt Leading Edges at High Mach Number

关键词:  内转式进气道  V字形钝化前缘平板  压敏涂料  激波干扰  流动分离

Key words:  Inward turning inlet  V-shaped plate with blunt leading edge  Pressure-sensitive paint  Shock interactions  Flow separation

摘要:

针对三维内转式进气道V字形唇口下游面临的严酷压力载荷问题，将唇口简化为V字形钝化前缘平板，在来流马赫数为6的条件下，采用数值模拟结合激波风洞压敏涂料测量方法，研究了V字形根部倒圆半径R与前缘钝化半径r之比（R/r=0~20）的平板表面压力演化特性。结果表明，随着R/r增大，V字形钝化前缘产生的三维波系结构发生变化，引起下游平板表面压力演变出4种类型。R/r较小时，V字形钝化前缘激波干扰产生的大范围流动分离，诱导形成了偏离中心线较远的分叉状高压区（Type Ⅰ，分叉型）；随着R/r增大，流动分离减弱，分叉状高压区逐渐消失，由透射激波扫掠壁面所形成的条带状高压和超声速射流对撞所形成的中心线高压区逐渐显露，依次出现过渡型（Type Ⅱ）、严酷型（Type Ⅲ）和渐匀型（Type Ⅳ）压力分布。平板上分叉型和过渡型的压力最大值仅为4.3~7.2p_∞（p_∞为来流静压），但V字形钝化前缘处的流场品质恶劣；严酷型的压力最大值随着射流对撞强度的增强而增大，最高可达19p_∞；渐匀型的压力最大值随着射流对撞强度的减弱，逐渐趋近于二维钝前缘平板产生的压力最大值4p_∞。

Abstract:

Severe pressure loads are usually encountered in the downstream of V-shaped cowl lips of three-dimensional inward-turning inlets. To reveal the flow physics of these pressure loads， a V-shaped plate with a blunt leading edge （VBLEP） was proposed. Numerical simulations and surface pressure measurements using the pressure-sensitive paint in a shock tunnel were performed with a freestream Mach number of 6. A series of VBLEPs with the R/r （i.e.， the crotch rounding radius R to the leading-edge radius r） ranging from 0 to 20 were investigated to focus on the surface pressure characteristics. With the increase of R/r， the three-dimensional shock configurations generated by V-shaped blunt leading edges （VBLE） change， causing the downstream plate surface pressure characteristics to evolve into four types. When R/r is small， the large-scale flow separation caused by the VBLE shock wave interactions induce the formation of a bifurcated high-pressure zone far away from the centerline （Type Ⅰ， “bifurcated type”）. With the increase of R/r， the flow separation weakens， the bifurcated high-pressure zone gradually disappears， the strip-shaped high-pressure zones formed by the transmitted shock wave sweeping the wall surface and the central high-pressure zones formed by the collision of the supersonic jet gradually reveal. Three pressure distribution types： “transition type” （Type Ⅱ）， “severe type” （Type Ⅲ） and “gradually uniform type” （Type Ⅳ） appear successively. The quality of the flow field at the VBLE for “bifurcated type” and “transition type” is deteriorated， although the maximum pressure for “bifurcated type” and “transition type” is merely 4.3~7.2p_∞ （p_∞ is the static pressure of incoming flow）. The maximum pressure of the “severe type” increases with the enhancement of the jet collision strength， which can reach up to 19p_∞. With the weakening of the jet collision strength， the maximum pressure of the “gradually uniform type” gradually approaches 4p_∞ （i.e.， the maximum pressure induced by a two-dimensional plate with a blunt leading edge）.